Wireguard for windows: routes are added even if remote server not reachable

[Jason A. Donenfeld]

You can adjust the route metric using `PostUp`, if you need:
https://git.zx2c4.com/wireguard-windows/about/docs/adminregistry.md

But having WireGuard automatically _shutoff_ due to unreachability
sounds like something with DoS security implications, so we're
unlikely to add that to the client. However you might be able to
trigger various rules to enable or disable WireGuard using other OS
facilities. https://git.zx2c4.com/wireguard-windows/about/docs/enterprise.md
may help.

Jason